1. Field of the Invention
The present invention pertains generally to the field of hoisting devices and more particularly relates to a hoist adapted for mounting to the bed of a cargo vehicle for facilitating loading and unloading of the vehicle.
2. State of the Prior Art
Numerous vehicle mounted hydraulically operated hoists of a general type similar to the present invention are known. Such hoists typically include a vertical mast mounted for rotation about its vertical axis, and a boom hinged at one end to the upper portion of the mast so that the free end of the boom can be raised and lowered. The boom is provided at its free outer end with a pulley or equivalent means over which is looped a hoist line. One end of the hoist line is anchored to the mast while a load may be attached to the other end of the line. A power actuating device, such as a hydraulic piston unit is connected between the mast and the boom, can be extended so as to apply upward leverage for lifting the free end of the boom together with a load suspended therefrom in relation to the stationary mast. Once raised, the suspended load may be swung laterally and moved in a circular arc by pivoting or rotating the mast about its vertical axis. The power actuator can then be retracted so as to lower the free end of the boom and drop the suspended load at a location removed from the pick-up point.
The prior art nearest to the present invention known to this applicant is the portable hoist disclosed by Harlan in U.S. Pat. No. 4,556,358.
The Harlan hoist is designed for mounting to the side wall of a truck bed rather than the floor of the truck bed. However, it is sometimes desirable to fasten the hoist directly to the bed of the pick-up particularly in modern pick-up trucks with side walls constructed of relatively thin sheet metal, and not capable of withstanding heavy lateral loads. In still other installations no lateral supports may be available and it is then necessary to secure the hoist only to a horizontal surface. While some others of the previously known hoists of this general type are designed for such mounting, the mounts are too complex and may require excessive modification to the vehicle. Further, these prior art hoists are not adapted to be readily and quickly removed from the pick-up truck bed so as to make space available for loading of cargo which does not require hoisting. Since a hoist mounted to a truck bed will necessarily obstruct and take up a substantial amount of space on the cargo bed, it is desirable to facilitate quick removal of as much of the hoist structure as possible when it is not needed, but without necessarily requiring complete detachment of the hoist base which is affixed to the truck bed. No hoist known to this applicant provides an adequate solution to the aforementioned needs.
A further difficulty encountered in the Harlan hoist and in others, is that the hoist line is anchored to the hoist mast or other portion thereof in a way which does not permit ready adjustment of the hoist line length. This shortcoming can cause considerable inconvenience and at times can make impossible certain hoisting jobs. While certain known hoists of the general type contemplated herein do allow for adjustment of the hoist line length, the means provided for this purpose have been unduly complex and sometimes not safely and easily operable by persons not especially trained in the hoist's operation. Thus, a further object of the present invention is to provide simple but safe and dependable means for anchoring the hoist line in a quickly and easily adjustable manner.
It is a still further object of the present invention to provide low cost and simple solutions to the aforementioned shortcomings of the prior art so as to make low-cost vehicle mounted hoists available to the average consumer for easy after-market installation on pick-up trucks and the like and which can be easily operated without skilled assistance, all without sacrifice in safety and reliability of the hoist.